Sodium chlorite does not ordinarily remain stable on storage. The anhydrous form is particularly hazardous; any sudden heating can result in "hot points" which can cause explosive decomposition into chloride, chlorate and further degradation products of chlorate. In the form of its hydrate NaClO.sub.2, 3H.sub.2 0 sodium chlorite is subject to changes in bulk volume and consistency unless the temperature is maintained at less than about 38.degree. C. At higher temperatures sodium chlorite dissolves in its water of hydration. Thus it loses it granulated form and, on subsequent cooling, congeals into a hard solid mass occupying only a fraction of the original bulk volume. This extremely inconvenient circumstance is experienced particularly in warm climates.
To the best knowledge of the present inventors, no satisfactory solution has been proposed to the problem of storing sodium chlorite without both hazards of decomposition by heat and of congealing into a solid mass.
It has been proposed to stabilize sodium chlorite in the anhydrous form by dilution with inert solid substances, for example sodium nitrate. But in order to obtain a satisfactory degree of stabilization in this manner it is necessary to use the inert material in amounts as high as about 30 to 40% based on the weight of sodium chlorite, thus inordinately diminishing the effective chlorite level.
Present applicants have established that there is no risk of decomposition if the sodium chlorite contains at least about 5% by weight of water. When a sodium chlorite product thus containing about 5% or more water is exposed to sudden heating, the heat is absorbed by the water in sufficient amount to prevent chemical disproportionation. However, as mentioned above, sodium chlorite containing at least 5% water congeals into a solid mass if it is submitted to a temperature above about 38.degree. C and subsequently cooled.